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Communication Dans Un Congrès Année : 2005

Windswept droplets

Résumé

A small droplet impacting a glass window usually remains stuck on the pane. How can we expel it? One possible solution consists in coating the glass surface with a hydrophobic layer. Another solution is to blow it off. We explore this last solution (partly combined with the first one). The droplet starts moving when the wind exceeds a threshold velocity, depending essentially on the surface wettability and the drop size. Above this threshold, the drift speed of the droplet results from a balance between aerodynamic drag and viscous dissipation near the contact lines. The results for different experimental conditions collapse on a master curve, once the wind speed is rescaled as a Weber number and the droplet velocity as a capillary number. While small droplets remain almost spherical caps, larger ones are strongly deformed and take the shape of a sausage, perpendicular to the wind direction. We finally determine the conditions in which satellite droplets are left at the rear of the moving drop, an issue crucial for blow drying processes.
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Dates et versions

hal-00163674 , version 1 (17-07-2007)

Identifiants

  • HAL Id : hal-00163674 , version 1

Citer

José Bico, François Besselièvre, Marc Fermigier. Windswept droplets. 58th Annual Meeting of the Division of Fluid Dynamics, Nov 2005, Chicago, United States. pp.151. ⟨hal-00163674⟩
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